Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$192.56	4.293%	$200.8266	$200.83	$200.85	$200.80
Purchase #2	$199.64	13.250%	$226.0923	$226.09	$226.10	$226.10
Purchase #3	$47.95	6.133%	$50.8908	$50.89	$50.90	$50.90
Purchase #4	$170.56	3.799%	$177.0396	$177.04	$177.05	$177.00
Purchase #5	$60.52	11.695%	$67.5978	$67.60	$67.60	$67.60
Purchase #6	$156.48	7.447%	$168.1331	$168.13	$168.15	$168.10
Purchase #7	$9.61	13.790%	$10.9352	$10.94	$10.95	$10.90
7 purchase totals =	$837.32		$901.5154	$901.52	$901.60	$901.40